Background - Neonatal cholestasis syndrome with an intra or extrahepatic origin has been associated to viral infections. The participation of the cytomegalovirus in the etiopathogenesis of neonatal hepatitis has been already known for some time, but only recently there have been indications that this virus may be one of the possible etiological factors for extrahepatic biliary atresia. Aims - To assess the prevalence of infection by cytomegalovirus in patients with intrahepatic cholestasis and extrahepatic cholestasis. To compare the clinical characteristics of the intrahepatic cholestasis and extrahepatic cholestasis groups with the cytomegalovirus serological results. Patients and Methods - This study consisted of 76 patients with neonatal cholestasis who were admitted between January 1980 and January 1999 when they underwent a cytomegalovirus serologic study using the ELISA method. A case note was kept on each patient with the following data: age of patient at admission, serologic result for cytomegalovirus, history of maternal infection, prematurity, fetal distress, birth weight, ponderal gain, choluria and fecal acholia. The final anatomic diagnosis of cholestasis was based on the results of an abdominal ultrasonography, a liver biopsy and its evolution. The patients were then divided into two groups: group I - intrahepatic cholestasis and group II - extrahepatic cholestasis. Each of these groups were then divided into two subgroups: subgroup A - positive serology (IgM) for cytomegalovirus and subgroup B - negative serology (IgM) for cytomegalovirus. Results - The frequency of positive serology (IgM) for cytomegalovirus was 29.4% in children with intrahepatic cholestasis and 28.5% in children with extrahepatic cholestasis. In comparison with group IIB, group IIA presented a higher rate of maternal infection history. The patients in group IIA demonstrated a delayed access to the service in comparison with group IA. The groups did not demonstrate any significant differences regarding the onset age of jaundice, choluria and fecal acholia, birth weight and ponderal gain. Conclusions - The positive (IgM) seroprevalence for cytomegalovirus in children with intrahepatic cholestasis and extrahepatic cholestasis is high. The history of maternal infection was more common in extrahepatic cholestasis patients with positive serology for cytomegalovirus. There was a delay in the referral of these patients which resulted in a late diagnosis and surgical treatment.